Remove offset_t typedef and use int64_t directly instead.

The name offset_t is easily confused with the standard off_t type and
*_t is POSIX reserved namespace if any POSIX header is included.

Originally committed as revision 15533 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/smacker.c

@@ -64,7 +64,7 @@ typedef struct SmackerContext {
     int buf_sizes[7];
     int stream_id[7];
     int curstream;
-    offset_t nextpos;
+    int64_t nextpos;
     int64_t aud_pts[7];
 } SmackerContext;